[A kin with a "silent" pseudocholinesterase gene (author's transl)].

After injection of short acting muscle relaxant suxamethonium on a 5-year-old boy during bronchography he was suffering from prolonged apnoe. Although using acetylthiocholin, butyrylthiocholin and benzoylcholin for tests we were not able to detect any activity of pseudocholinesterase in the patient's serum, Since there was no evidence of hepatic disease or hypoproteinemia, we supposed a genetically caused deficiency of serumcholinesterase. Examinations done on 18 members of this kin showed a complete absence of serumcholinesterase on 3 children (homozoygotes for "silent gene") and a significant decrease of pseudocholinesterase on 6 persons. It was not possible to detect the "silent gene" by counter immunelectrophoresis. The half value time after injection of purified human serumcholinesterase was between 8 to 9 days. Genetic aspects and clinical problems of the serumcholinesterase deficiency are discussed.